The Boston typewriter was produced during the latter part of the 19th century in (you guessed it) Boston. It was invented by Daniel E. Kempster and produced ca.1888 by The Boston Type-Writer Company. As far as index typewriters go, most that I've come across are small compared to the Boston. The grade of the iron and wood are notably better in quality than its contemporaries, too. The Boston typewriter is a serious piece of industrial era machinery.
Have one for sale? Please email me at Antikey.Chop@gmail.com